Variations In Human Color Vision

In 1794, John Dalton, the celebrated chemist, offered a series of astute observations about his own color perceptions. He noted, for instance, that the spectrum appeared to him to contain just three colors (yellow, blue, and purple) and that flowers that appeared pink to others seemed to him "an exact sky blue.'' Dalton eventually discovered that many other individuals shared his atypical color perceptions and he was led to offer a hypothesis to explain the condition based on the presumed presence of some unusual intraocular filter. Retrospective analysis shows that Dalton suffered from deuteranopia, a common congenital color vision defect that affects about 1% of all males. Dalton was not the first to learn of defective color vision among humans, and his explanation of the source of the defect was wrong, but his detailed descriptions were very instrumental in initiating a long series of examinations of color defect that continue to the present day. Studies of color vision defects, and of other individual variations in color vision, have provided significant insights into the biology of color vision. In addition to the congenital color vision defects, color vision change may be acquired through a wide variety of visual system pathologies as well as senescent changes occurring in the visual system.

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

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